Use of sulphonated alkyl phenol formaldehydes in the stabilization of ashphaltenes in crude oil

ABSTRACT

Sulfonated compounds prepared by reacting at least one compound selected from the group consisting of formula (I) and (II), with gaseous SO 3  in an equimolar ratio:  
                 
 
wherein each Ph represents a phenol residue, n represents a number of from 2 to 12 and each R independently represents a moiety selected from the group consisting of C 3-24  alkyl groups, C 6-12  aryl groups, C 6-12  hydroxyaryl groups, and C 7-12  aralkyl groups; and methods of stabilizing asphaltenes in crude oil with sulfonated compounds are described.

This invention relates to certain sulfonated alkylphenol formaldehydesand to their use for stabilizing asphaltenes in crude oil and to aprocess for preventing the precipitation of asphaltenes in crude oils.

Crude oil is a complex mixture of various paraffinic and aromatichydrocarbons in which the individual constituents have very differentchemical and physical properties. Accordingly both readily volatile,low-viscosity constituents and wax-like, high-viscosity fractions areobtained in the distillation of crude oil. The second of these twogroups includes petroleum resins and, to a predominant extent,asphaltenes which are colloidally dispersed in the oil phase.

The asphaltenes consist of a mixture of various saturated, unsaturatedand aromatic hydrocarbons, more particularly naphthalene derivatives.They also contain heterocyclic hydrocarbons which, in part, also containcomplexed metal ions. In addition, asphaltenes are rich in sulfur,nitrogen and oxygen compounds. Because of their complex composition,asphaltenes are generally characterized on the basis of theirsolubility. Thus, the petroleum fraction insoluble in heptane orpentane, but soluble in toluene is referred to as asphaltenes, the“dissolution” of asphaltenes involving a complex process for which therehas as yet been no complete theoretical explanation (cf. E. Y. Scheu, O.C. Mullins, Asphaltenes—Fundamentals and Applications, Plenum Press, NewYork, 1995, Chapter I and Chapter III).

Asphaltenes are present as micelle colloids in the oil phase of crudeoil, the individual micelles consisting of several different molecules.The micelles vary in size according to the temperature and compositionof the oil phase. For example, it is known that relatively lightaromatic hydrocarbons in crude oil stabilize the asphaltene micelles.Under the conditions prevailing in petroleum production, however, theasphaltenes are often precipitated which results in the formation ofhighly viscous, wax-like or solid residues on the surface of theproduction units and the petroleum-containing formation surrounding thewell. The asphaltene residues block the pores of the formation whichleads to a noticeable reduction in the production rates and, in theworst case, can make production completely impossible. Asphalteneresidues on the surfaces of the production units, for example thedelivery tube or the casing walls of pipelines or separators, can alsoconsiderably reduce production.

Accordingly, there are various known methods for keeping asphaltenesdispersed in crude oil and for preventing their precipitation. DE 197 09797 describes synergistic mixtures of alkyl phenol formaldehyde resinsand certain alkoxylated amines as asphaltene dispersants. It is knownfrom U.S. Pat. No. 4,414,035 that alkyl aryl sulfonic acid derivatives,for example dodecyl benzenesulfonic acid, disperse asphaltenes in crudeoils.

However, it has often been found in practice that known auxiliaries forstabilizing asphaltenes differ very considerably in their effectivenessaccording to the nature and origin of the crude oil. This isattributable in particular to the complex and highly variable structureof the asphaltenes. Accordingly, efforts have been made to find newasphaltene stabilizers. In addition, known asphaltene stabilizers areoften either toxic and/or ecologically unsafe. Because of this, it ispreferred to avoid using them both for reasons of environmental safetyand in the interests of safety at work.

Accordingly, the problem addressed by the present invention was toprovide effective alternatives to the stabilizers known from the priorart for stabilizing asphaltenes in crude oils, despite very differentcrude oil qualities. It has been found that certain sulfonated alkylphenol formaldehydes solve this problem.

In a first embodiment, therefore, the present invention relates to theuse of products obtainable by sulfonation of compounds corresponding toformula (I) or (II):

in which n is a number of 2 to 12 and R is a C₃₋₂₄ alkyl, C₆₋₁₂ aryl orhydroxyaryl or C₇₋₁₂ aralkyl group, as stabilizers for asphaltenes incrude oil. In addition, Ph in formula(l) and (II) is a phenol residue.

The sulfonation products used in accordance with the invention areobtained by sulfonation of compounds known per se corresponding togeneral formulae (I) and/or (II). These starting products are known, forexample, from DE 197 09 797 A1. Reference is made here to formulae (I)and (II) in claim 1 of DE 197 09 797 A1, to the disclosure on page 2,lines 40 to 44 and to the disclosure on page 3 of that document. Thedisclosures of those passages are specifically included in thedisclosure of the present application. Formulae (I) and (II) in DE 19709 797 are identical with those of the present application. Thecompounds in question are resins which are obtainable, for example,under the name of Dowfax DM 645 (Dow Chemicals).

The educts corresponding to formulae (I) and (II) are sulfonated inknown manner with gaseous SO₃. According to the invention, however, thesulfonation products are not neutralized, but are present as free acids.The sulfonation of the educts is preferably carried out by a continuousprocess in a falling film reactor. The gaseous sulfur trioxide isproduced in situ by pyrolysis of pure sulfur. The polyalkyl formaldehyderesin used is preferably reacted with sulfur trioxide in an equimolarratio. The reaction itself advantageously takes place at a temperatureof 75 to 80° C. The end product is preferably not neutralized. Theproducts according to the invention are obtained in the form of aqueoussolutions which may be directly formulated and used as asphaltenedispersants without any further steps. The sulfonated productssurprisingly exhibit distinctly better properties as asphalteneinhibitors or asphaltene stabilizers than the compounds known from theprior art or mixtures thereof according to the teaching of DE 197 09 797A1.

Crude oil in the context of the present invention is understood to bethe unrefined petroleum coming directly from the ground. This unrefinedpetroleum consists of complex mixtures of, predominantly, hydrocarbonswith densities of 0.65 to 1.02 g/cm³ and calorific values of 38 to 46MJ/kg. The boiling points of the most important constituents of crudeoil are in the temperature range from 50 to 350° C. (cf. Römpp,Chemielexikon, Vol. 2, 1997, pages 1210 to 1213).

The use of the sulfonated alkylphenol formaldehydes in accordance withthe invention, i.e. their addition to crude oils, effectively preventsthe precipitation of asphaltenes and the formation of residues. In orderto prevent the precipitation of asphaltenes, it is of advantage to addthe sulfonated alkylphenol formaldehydes to the crude oil in quantitiesof 50 to 2500 ppm, preferably in quantities of 100 to 1000 ppm and moreparticularly in quantities of 150 to 500 ppm (active substance).

The present invention also relates to a process for preventing theprecipitation of asphaltenes from crude oils, characterized in thatsulfonated alkylphenol formaldehydes corresponding to the foregoingdescription are added to the crude oils as stabilizers in quantities of100 to 2500 ppm.

The present technical teaching also encompasses the use of thesulfonated alkylphenol formaldehydes in the form of dilute solutions inaromatic solvents, preferably toluene. These dilute solutions containthe polyester amides in quantities of preferably 2 to 50% by weight,more preferably 2 to 20% by weight and most preferably 2 to 15% byweight. Corresponding formulations may also contain other additives,such as corrosion inhibitors or defoamers.

EXAMPLES

Production of the Sulfonation Products:

The educts were sulfonated by a continuous process in a falling filmreactor. The gaseous sulfur trioxide was produced in situ by pyrolysisof pure sulfur. The polyalkyl formaldehyde resin used was reacted withsulfur trioxide in an equimolar ratio. The reaction itself was carriedout at a temperature of 75 to 80° C. The end product was notneutralized. The active substance content as measured by Eptontitration, the molecular weight and the acid number were determined ascharacteristics.

Typical values for a resin based on Dowfax DM 650 are shown by way ofexample below: Molecular Additive Acid value weight [g/mol] Activesubstance content [%] A1 85-90 641 62-66Testing of the Dispersing Properties:

The test is based on the fact that asphaltenes are soluble in aromatichydrocarbons, but not in aliphatic hydrocarbons. Accordingly,dispersants can be tested by dissolving the oil or extracted asphaltenesin an aromatic solvent and then adding a nonaromatic solvent to producea deposit. Since asphaltenes are dark in color, the size of the depositcan be determined by UV-spectroscopic measurement of the supernatantliquid.

Dispersing Test—Procedure

-   a) A 20% solution of isolated asphaltenes in toluene is prepared;-   b) 9.5 ml heptane as precipitant for asphaltenes, 0.5 ml of the    asphaltene solution in toluene and the corresponding quantity of    dispersant solution for the required concentration are mixed and    thoroughly shaken in a 10 ml graduated glass tube;-   c) a test tube without any dispersant solution is prepared as a    negative sample and the solvent heptane is replaced by toluene as a    positive sample; two commercial products (Anticor DSA 800 and 711)    were included in the tests for further comparison;-   d) the test tubes were observed for 3 hours and the precipitation    time of the asphaltenes was recorded, the sediment collecting at the    bottom of the test tubes;-   g) evaluation of the sediment volume and appearance of the solution    was carried out in comparison with the positive and negative    samples. Evaluation of the sediment volume was based on a scale of 1    to 3 where 3 represents the largest volume.

The results of the precipitation tests at three concentrations ofvarious formulations A to H according to the invention are set out inthe following Table. TABLE 1 Asphaltene test for various formulationsFormulation 100 ppm 500 ppm 1000 ppm Negative sample T = 30 mins T = 30mins T = 30 mins. SV = 3 SV = 3 SV = 3 A No SV No SV No SV B No SV No SVT = 30 mins. SV = 2 C No SV No SV T = 30 mins. SV = 2 D No SV No SV NoSV E No SV No SV No SV F No SV No SV No SV G T = 45 mins. No SV No SV SV= 1 H No SV No SV No SV Positive sample No SV No SV No SV Anticor DSA800 T = 2 h T = 16 h No SV T = 1-2 SV = 1 Anticor DSA 711 T = 60 mins. T= 16 h No SV SV = 2 SV = 1T = precipitation time,SV = sediment volume (3 = maximum)

In order to be able to compare the results of the spectroscopicanalysis, the absorption values of the experimental formulations weredivided by the corresponding value of the positive sample (puretoluene)—shown in the Tables as relative absorption. The nearer thevalues are to 1.0, the better the effect of the dispersant formulation.The values are set out in the following Table. TABLE 2 Relativeabsorption values of the asphaltene solutions Formulation 100 ppm 500ppm 1000 ppm A 0.81 0.85 0.86 B 0.79 0.81 0.72 C 0.76 0.79 0.73 D 0850.87 0.89 E 0.84 0.82 0.86 F 0.79 0.80 0.84 G 0.76 0.79 0.83 H 0.82 0.860.87 Positive sample 1 1 1 Anticor DSA 800 0.74 0.76 0.78 Anticor DSA711 0.75 0.78 0.78

1-5. (canceled)
 6. A method comprising: (a) providing one or moresulfonated compounds prepared by sulfonating one or more compoundscorresponding to the general formulae (I) or (II):

wherein each ph represents a phenol residue, n represents a number offrom 2 to 12 and each r independently represents a moiety selected fromthe group consisting of C₃₋₂₄ alkyl groups, C₆₋₁₂ aryl groups, C₆₋₁₂hydroxyaryl groups, and C₇₋₁₂ aralkyl groups; and (b) combining the oneor more sulfonated compounds and a crude oil composition comprising oneor more asphaltenes:
 7. The method according to claim 6, wherein the oneor more sulfonated compounds are combined with the crude oil compositionin an amount of from 50 to 2500 ppm.
 8. The method according to claim 6,wherein the one or more sulfonated compounds are combined with the crudeoil composition in an amount of from 100 to 1000 ppm.
 9. The methodaccording to claim 6, wherein the one or more sulfonated compounds arecombined with the crude oil composition in an amount of from 150 to 500ppm.
 10. The method according to claim 6, wherein the one or moresulfonated compounds are combined with the crude oil composition in theform of an aromatic solution.
 11. The method according to claim 10,wherein the aromatic solution comprises toluene.
 12. A process forproducing a sulfonated compound, said process comprising: (a) providingat least one compound selected from the group consisting of formula (I)and (II):

wherein each Ph represents a phenol residue, n represents a number offrom 2 to 12 and each R independently represents a moiety selected fromthe group consisting of C₃₋₂₄ alkyl groups, C₆₋₁₂ aryl groups, C₆₋₁₂hydroxyaryl groups, and C₇₋₁₂ aralkyl groups; and (b) reacting the atleast one compound with gaseous SO₃ in an equimolar ratio.
 13. Theprocess according to claim 12, wherein the at least one compound isreacted with gaseous SO₃ in a falling film reactor.
 14. The processaccording to claim 12, wherein the at least one compound is reacted withgaseous SO₃ at a temperature of from 75 to 80° C.
 15. The processaccording to claim 12, wherein the at least one compound is reacted withgaseous SO₃ in a falling film reactor at a temperature of from 75 to 80°C.
 16. A sulfonated compound prepared by a process comprising: (a)providing at least one compound selected from the group consisting offormula (I) and (II):

wherein each Ph represents a phenol residue, n represents a number offrom 2 to 12 and each R independently represents a moiety selected fromthe group consisting of C₃₋₂₄ alkyl groups, C₆₋₁₂ aryl groups, C₆₋₁₂hydroxyaryl groups, and C₇₋₁₂ aralkyl groups; and (b) reacting the atleast one compound with gaseous SO₃ in an equimolar ratio.
 17. Thesulfonated compound according to claim 16, wherein the at least onecompound is reacted with gaseous SO₃ in a falling film reactor.
 18. Thesulfonated compound according to claim 16, wherein the at least onecompound is reacted with gaseous SO₃ at a temperature of from 75 to 80°C.
 19. The sulfonated compound according to claim 16, wherein the atleast one compound is reacted with gaseous SO₃ in a falling film reactorat a temperature of from 75 to 80° C.